1. Field of the Invention
The present application generally relates to the field of semiconductor light-emitting devices, and more particularly, to a semiconductor light-emitting device having several non-parallel etched surfaces.
2. Description of the Prior Art
A light-emitting diode (LED) is a solid-state semiconductor light source that is fabricated with semiconductor materials and capable of transforming electricity into light energy efficiently. LEDs are used in applications as diverse as: replacements for aviation lighting, automotive lighting (particularly for indicators), in traffic signal lights, billboards, the backlight of the display and so on. The compact size of LEDs has allowed new text and video displays or sensor devices to be developed, with their quick switching rates being very useful for advanced communication technology.
A structure of a conventional light-emitting device generally includes a substrate, an epitaxial structure disposed on the substrate, a p-side electrode pad electrically connected to a p-type semiconductor layer located in the epitaxial structure, an n-side electrode pad electrically connected to an n-type semiconductor layer located in the epitaxial structure, an active layer disposed between the p-type semiconductor layer and the n-type semiconductor layer. In addition, a transparent conductive layer (TCL) is usually disposed between the p-side electrode pad and the p-type semiconductor layer in order to create an ohmic contact.
A semiconductor light-emitting device, includes a substrate including a main surface and an exposed surface, wherein the main surface and the exposed surface include concavo-convex structures; an epitaxial structure disposed on the main surface of the substrate including a first type semiconductor layer, a light-emitting layer, a second type semiconductor layer, a buffer layer disposed between the first type semiconductor layer and a nucleation layer and the nucleation layer disposed between the substrate and the buffer layer; an electrode structure disposed on the epitaxial structure; wherein an upper part of the first type semiconductor layer includes a first sidewall including a first etched surface so that a first angle between the first etched surface and the exposed surface is acute; wherein a bottom part of the first type semiconductor layer, the buffer layer and the nucleation layer includes a second sidewall including a second etched surface so that a second angle between the second etched surface and the exposed surface is also acute, which is narrower than the first angle, wherein an angle inside the epitaxial structure between the first etched surface and the second etched surface is between 90° and 180° , wherein highest light intensity is usually at emission angles of 60° and 120° and the light intensity is gradually reduced toward emission angles of 0° and 180°.